The incident marked the 154th mass shooting in 2018, according to the nonprofit Gun Violence Archive, which tracks shootings in the US. To put this into perspective, we are 177 days into the year, which means the US has had nearly as many mass shootings as days in 2018.

There is no broadly accepted definition of a mass shooting. Gun Violence Archive defines a mass shooting as a single incident in which four or more people, not including the shooter, are "shot and/or killed" at "the same general time and location."

The government also doesn't have an official definition. In 2013, a report from the Congressional Research Service, known as Congress's think tank, described mass shootings as those in which shooters "select victims somewhat indiscriminately" and kill four or more people — a higher bar than Gun Violence Archive's, as it doesn't take injuries into account.